<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>优先级</title>
</head>
<style>
   p strong{
       color: aqua!important;
   } 
   strong.mycolor{
       color: blueviolet;
   }
   
   .father strong{color: yellow;}
   p.father strong{color: orange;}
   p.father .blue{color: gold;}

   #header strong{
       color: green;
   }
   #header strong.blue{color: red;}
</style>
<body>
   <p class="mycolor" id="header">  which color?</p>
   <p class="father" id="header">
       <strong class="blue">文本颜色</strong>
   </p>
</body>
</html>